1. Last two years of CMS physics study in Peking University
7/12/1997
Chinese-French Workshop, Beijing,
Last two years of CMS physics study in Peking University .

2. CMS-PKU group Professor: Lecturer: Graduate students: Y. Ban Y. Mao
7/12/1997
Chinese-French Workshop, Beijing,
CMS-PKU group
Professor:
Y. Ban
Y. Mao
S. Qian
Lecturer:
S. Wang
Graduate students:
Z. Yang
L. Liu
S. Guo
Sijin QIAN CMS Physics study in Peking University

3. Outline Heavy Quarkonia production and polarization. Other works
7/12/1997
Chinese-French Workshop, Beijing,
Outline
Heavy Quarkonia production and polarization.
Motivation.
Event generation and simulation.
Polarization parameter extraction: 2 methods.
Other works
CMS Analysis Note 2006/094 “J/y  m+m- Reconstruction in CMS” was approved.
Suggestion on HLT J/y trigger
Comparison between ORCA and CMSSW
Ongoing work and the planned new physics topics
Summary
Sijin QIAN CMS Physics study in Peking University

4. Heavy Quarkonia production and polarization
Chinese-French Workshop, Beijing,
Heavy Quarkonia production and polarization
Sijin QIAN CMS Physics study in Peking University

5. Motivation (1) Conventional Mechanism of Heavy Quarkonia:
Chinese-French Workshop, Beijing,
Motivation (1)
Conventional Mechanism of Heavy Quarkonia:
* parton interaction produces quark pair, quark pair bind into quarkonia.
* color and spin is conserved during binding. The quarkonia is color-singlet, so the quark pair must be color-singlet too.
-> Color Singlet Model (CSM)
1-2 orders of magnitude discrepancy between CSM prediction and CDF Result
Prompt charmonium production Bottomonium production
black dot: CDF experiment
dashed line: color-singlet
solid line : NRQCD fit
J/Y： PRL, 79 (1997) 572
 ： PRL, 88 (2001)
Sijin QIAN CMS Physics study in Peking University

6. Motivation (2) New Mechanism of Heavy Quarkonia (COM):
Chinese-French Workshop, Beijing,
Motivation (2)
New Mechanism of Heavy Quarkonia (COM):
Parton interaction produces quark pair (ccbar), quark pair can be color-octet
Quark pair can change color and spin through emitting gluon and then bind into quarkonia (J/psi, psi’...)
-> Color Octet Mechanism (COM)
Production of Quarkonia can be factored into 2 steps:
Creation of the quark pair, can be color-singlet or color-octet
Quark pair bind into quarkonia
Short Distance Coefficient:
Creation of quark-antiquark pair.
This step is independent of final product.
Can computed pertubatively
Long Distance Matrix Element
(LDME):
How likely the quark pair will
bind to the quarkonia.
Sijin QIAN CMS Physics study in Peking University

7. Motivation (3) => Polarization puzzle NRQCD prediction
Chinese-French Workshop, Beijing,
Motivation (3)
=> Polarization puzzle
NRQCD prediction
PRL, 85(2000) 2886
a=+1: transversely polarized
a=-1: longitudinally polarized
CDF run 1 results q m+ m-
J/Y direction
in lab frame
m+ direction
in J/Y rest frame
CDF run 2 results
Sijin QIAN CMS Physics study in Peking University

8. Quarkonia polarization @ CMS
Chinese-French Workshop, Beijing,
Quarkonia CMS
Higher luminosity:
better statistics in general
especially important for ϒ which is expected to be described better by NRQCD
Higher collision energy:
larger cross-section
higher pT region reached
Better Muon Measurement
preferable for J/Ψ → μ+μ− and ϒ → μ+μ−
Sijin QIAN CMS Physics study in Peking University

9. Simulation of Heavy Quarkonia
Chinese-French Workshop, Beijing,
Simulation of Heavy Quarkonia
PYTHIA in CMKIN_6_0_0
 include both CSM and COM
Reproduce CDF Result
 to confirm our understanding
 to tune the NRQCD parameters
Quarkonia simulation
 keep the same NRQCD parameters and increase to LHC collision energy, 14TeV
 FAMOS for CMS simulation
Sijin QIAN CMS Physics study in Peking University

10. Reproduce CDF Result J/Y  * CTEQ5L PDF * √s =1800GeV
Chinese-French Workshop, Beijing,
Reproduce CDF Result
J/Y 
* √s =1800GeV
* |y|<0.4 for 
* CTEQ5L PDF
* LDME from hep-ph/
(J/Y) & PRD ()
* ||<0.6 for J/Y
* 100k MC events
Sijin QIAN CMS Physics study in Peking University

11. Chinese-French Workshop, Beijing, 14-12-2006
FAMOS
Normalized 1fb-1 integral luminosity, the reconstructed J/y’s pT distribution may be like this :
1M MC events
NRQCD parameters fitted from CDF
Through FAMOS
Enough statistics in first 1fb−1, 4 months’ run in 1032cm-2s-1
About 3000 events per
GeV at pT=50GeV/c
Sijin QIAN CMS Physics study in Peking University

12. Measurement of the polarization
Chinese-French Workshop, Beijing,
Measurement of the polarization
Template fit: fit to a weighted sum of two MC templates: transverse polarization template and longitudinal polarization template.
: fully transverse polarization
: fully longitudinal polarization
Sijin QIAN CMS Physics study in Peking University

13. Template fit Reconstruction efficiency a = -1 generation
Chinese-French Workshop, Beijing,
Template fit
a = -1 generation
a = +1 generation
Reconstruction efficiency
a=-1 reco template
a=+1reco template
Normalize to the same integral luminosity as signal events.
Then fit with:
To do the normalization we need to know the reconstruction efficiency, but the efficiency depends on a. So we first try a loop fitting.
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14. Extraction Method (1): Loop Fit
Chinese-French Workshop, Beijing,
Extraction Method (1): Loop Fit
Normalize to the MC templates
a=0 efficiency
Weighted efficiency
Signal Pt distribution
Weighted efficiency ……
Solid Line is alpha input, data point is alpha fit value
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15. Extraction Method (2): Neural Network Fit
Chinese-French Workshop, Beijing,
Extraction Method (2): Neural Network Fit
deviation
Neural network well fits input value. The result is not dependent on a and pT.
These two methods can cross-check each other.
Sijin QIAN CMS Physics study in Peking University

16. Differential cross-section
Chinese-French Workshop, Beijing,
Differential cross-section
For each PT bin, the reconstruction efficiency can be calculated as a weighted sum of the efficiencies of the two MC template. The weight is from polarization fit.
Sijin QIAN CMS Physics study in Peking University

17. Backgrounds B mesons’ decay include J/y ccbar→μμ x bbbar →μμ x
Chinese-French Workshop, Beijing,
Backgrounds
B mesons’ decay include J/y
ccbar→μμ x
bbbar →μμ x
General QCD, W+jets, Z+jets
Minbias events
The most important background is from B mesons’ decays. The last four backgrounds don’t have a peak on dimuon’s invariant mass.
Sijin QIAN CMS Physics study in Peking University

18. Physics Letters B, Review of Particle Physics, Vol.592/1-4 (2004) 781.
Chinese-French Workshop, Beijing,
B production: B0
39.7±1.0% B+
B0s
10.7±1.1%
b-baryon
9.9±1.7% BC －
B decay branch ratio
J/y + anything
1.16±0.10%
Y(2S) + anything
(4.8±2.4) ×10-3
Chi_c1 + anything
1.5±0.5%
Physics Letters B, Review of Particle Physics, Vol.592/1-4 (2004) 781.
Prompt J/psi events are the background for B meson physics, so we can learn much from B studies. The basic idea is to use the vertex cut.
Sijin QIAN CMS Physics study in Peking University

19. Chinese-French Workshop, Beijing, 14-12-2006
Ongoing work and plan
Re-do the study in CMSSW.
Trigger influence study.
Study the backgrounds, may learn from B physics groups.
1 Million full simulation events: Need much computing power and nearly 2T GB storage. By EUChinaGrid? Or to convince CMS to use higher version of Pythia?
This may be one of the first CMS papers, if everything would go well.
Sijin QIAN CMS Physics study in Peking University

20. Chinese-French Workshop, Beijing, 14-12-2006
Other Works
Our first CMS AN 2006/094 “J/y  m+m- Reconstruction in CMS” was finally approved in last week
Sijin QIAN CMS Physics study in Peking University

21. Chinese-French Workshop, Beijing, 14-12-2006
AN 2006/094
We analyzed the dataset bt03_B0sJPsiPhi at CNAF, which contains B0sJ/y(m+m- )f(K + K -) events.
We focused on the J/y m+m- sub-process.
J/y eff. vs pT
Invariant mass
J/y eff. vs Eta
Sijin QIAN CMS Physics study in Peking University

22. L1 and HLT trigger rates Triggering rates L1 Trigger
Chinese-French Workshop, Beijing,
L1 and HLT trigger rates
Triggering
rates
L1 Trigger
L1 single muon bit
8.93%
L1 double muon bit
33.7%
L1 any muon bit
36.7%
L1 decision
36.9%
HLT Trigger
Bit HLTmuons: L3MuTrigger
0.20%
Bit double_muons: CombinatorialAndTrigger
0.44%
HLT decision
Bit 35 or 38 any muon was triggered
0.63%
HLT global decision (cumulative after L1 and HLT)
0.66%
Offline reconstruction
Efficiency (i.e. offline) for events that pass HLT
68%
Overall efficiency (L1*HLT*Offline)
0.45% =0.66%*68%
Mass resolution (for J/y that passed HLT)
0.96%
Sijin QIAN CMS Physics study in Peking University

23. Chinese-French Workshop, Beijing, 14-12-2006
Triggering effects
PT distribution of the J/y h distribution of the J/y
at different level: generator level, all reconstructed events without decision, L1 decision and HLT decision.
Why HLT rejects high pT J/psi events?
Sijin QIAN CMS Physics study in Peking University

24. HLT muon trigger has a bug in muon track isolation algorithm.
Chinese-French Workshop, Beijing,
HLT muon trigger has a bug in muon track isolation algorithm.
DR distribution
DR=0.24
Events passed HLT decision
high J/psi PT (> 35 GeV/c) events
Sijin QIAN CMS Physics study in Peking University

25. Chinese-French Workshop, Beijing, 14-12-2006
Tracker Isolation
In order to isolate the muons from jets, which accompanied by nearby particles.
It calculate the SpT of fully reconstructed tracks (charged particles) in a cone (DR=0.24) around the direction of the L3 muon, neglecting the contribution from the muon itself.
If a high pT muon is reconstructed inside the cone around another muon, SpT will be very large, and the HLT isolation criteria will not be satisfied and the event will be rejected.
So all the muon tracks in the cone should be neglected. This will be done in CMSSW.
Sijin QIAN CMS Physics study in Peking University

26. Chinese-French Workshop, Beijing, 14-12-2006
Study on a possible HLT J/y trigger (was just reported in the CMS Standard Model meeting on this Monday)
Sijin QIAN CMS Physics study in Peking University

27. Chinese-French Workshop, Beijing, 14-12-2006
HLT J/psi Trigger
L2 Muon
Producer
L2 J/Psi Filter
L3 Muon
L3 J/Psi Filter
The trigger may have two steps: one filter for L2 muons (stand-alone muons) and one for L3 muons (global muons).
J/Psi filter:
dimuon cuts on PT, Eta
dimuon’s invariant mass window
(2.0GeV, 4.2Gev) for L2 muons
(3.0GeV, 3.2GeV) for L3 muons
The PT cut should correspond to L1 muon trigger.
Sijin QIAN CMS Physics study in Peking University

28. Trigger rates with different PT cuts
Chinese-French Workshop, Beijing,
Trigger rates with different PT cuts
We both studied CSM and COM J/psi. Here: Luminosity = 1033 cm-2s-1
Cut
(mass window)
CSM (Hz)
COM (Hz) L2 L3
Muon PT>3GeV/c
(3.0GeV,3.2GeV)
2.57
2.20
34.1
28.8
Muon PT>4GeV/c
1.72
1.34
19.1
14.5
Muon PT>5GeV/c
0.998
0.872
8.93
7.61
Muon PT>6GeV/c
0.598
0.564
4.02
3.73
Muon PT>7GeV/c
0.401
0.383
1.82
1.77
Sijin QIAN CMS Physics study in Peking University

29. Possible trigger conditions at different luminosities
Chinese-French Workshop, Beijing,
Possible trigger conditions at different luminosities
For Luminosity = 1029 cm-2s-1
L1 trigger may should be loose
For Luminosity = 1030 cm-2s-1
L1 trigger
For Luminosity = 1031 cm-2s-1
L1 trigger, PT cut 3GeV with mass window
For Luminosity = 1032 cm-2s-1
L1 trigger, PT cut 5GeV with mass window
For Luminosity = 1033 cm-2s-1
L1 trigger, PT cut 7GeV with mass window
Sijin QIAN CMS Physics study in Peking University

30. Pay attention to the status of CMSSW muon reconstruction
Chinese-French Workshop, Beijing,
Pay attention to the status of CMSSW muon reconstruction
Sijin QIAN CMS Physics study in Peking University

31. Comparing CMSSW with ORCA
Chinese-French Workshop, Beijing,
Comparing CMSSW with ORCA
Stand-alone muons
Genrated
ORCA
CMSSW_1_1_0
Muon PT J/y PT
Muon Eta J/y Eta
Sijin QIAN CMS Physics study in Peking University

32. J/y’s invariant mass CMSSW_1_1_0 ORCA
Chinese-French Workshop, Beijing,
J/y’s invariant mass
CMSSW_1_1_ ORCA
ORCA implements Vertex-Update in stand-alone muon reconstruction, while CMSSW doesn’t. It will be implement soon.
Sijin QIAN CMS Physics study in Peking University

33. Chinese-French Workshop, Beijing, 14-12-2006
Global muons
In 1_1_0 to 1_2_0_pre8, there was a problem in MuonTrajectoryCleaner. So that the global muons are more than Stand-alone muons. It was fixed in CMSSW_1_2_0_pre9.
But CMSSW_1_2_0_pre9 has some problems in stand-alone muons, only reconstruct half than CMSSW_1_1_0.
Stand-alone muon
Global muon
Generated
4006
ORCA_8_13_3
3352
3194
CMSSW_1_1_0
3257
4186
CMSSW_1_2_0_pre2
3202
4011
CMSSW_1_2_0_pre9
1541
1346
We reported it last Sunday, and it was solved for 1_2_0 early this week. So we hope that we can use final CMSSW_1_2_0 to do some physics study.
Sijin QIAN CMS Physics study in Peking University

34. Ongoing and future works
Chinese-French Workshop, Beijing,
Ongoing and future works
More detailed study on the HLT J/y trigger in CMSSW. The HLT official production of 1 Million prompt J/y (still only CSM) will come out soon. The .cfg file is: Configuration/CSA06Production/data/Jpsi_mumu_sim_digi_OnSel.cfg
Study on using J/y for calibration.
Other physics topics (H  AA  4l, Top quark polarization and parity violation, etc.)
Wish can collaborate with French colleagues for new topics
Sijin QIAN CMS Physics study in Peking University

35. Thank you ! Chinese-French Workshop, Beijing, 14-12-2006
Sijin QIAN CMS Physics study in Peking University